LP#1562061 Make Lost/Long-overdue billings exclusive

LP#1562061 Make Lost/Long-overdue billings exclusive

It would be nice if, for purposes of status, we could mark long-
overdue items as lost, but without causing any duplicate billings.

This code interprets any long-overdue/lost billing as "final" for
automation purposes, and then only generates bills (and potentially
reopens xacts) in cases where no "final" billing has yet taken
place (based on stopfines).

(indenting left in place for readability, handled in follow-up)

Signed-off-by: Dan Wells <dbw2@calvin.edu>